def search4vowels(word: str)->set:
    '''search4vowels ： return vowels times'''    
    vowels = list('aeiou')
    found = dict()
    print(vowels)
    for letter in word:
        if letter in vowels:
            found.setdefault(letter, 0)
            found[letter] = found[letter] + 1
    return found


print(search4vowels('hello world'))
 